Chicken or the Egg??? Which way to process?

[BlaineW]

Looking for a first instinct suggestions on how to process this. Without going into too much detail here is what I have.

Roughly a cylinder w/ one side needing to be milled, other turned.

A .002 total tolerance partial 12" dia that has to be circle interpolated and is my datum and is only about .075 wide.

On the other side of the part, roughly 3" away, a .0006 total tolerance 7" dia and a duplicate another 4" away, both roughly 1" wide, and both of which have to be held within .001 true position to my datum.

Million $ question is, mill datum first, then figure out way to hold on the small snap diameter to create .0006 dias...then how do i hold in such a way to manage .001 true position on a .075 wide surface.

Or do I create .0006 first and then use that to create my more open tolerance that my datum has. Then how do I hold on it without marking up my surface and also meet the .001 true position.

I know this is all kind of general without seeing the part...(government work and all that) but 4 of us can't seem to agree on how to do it, so I'm looking for more opinions.

Thanks

 

[mfgenggear]

BlaineW

what type of material?

Hardness required before machined and after?


can you post a pdf file, but remove your customers name & part number.

 

[plasgears]

Machine the rougher finish and fixture on that with a collett. then proceed to the finer finished zone.